1. Field of the Invention
The invention, as covered by Ref4, Non-provisional patent application Ser. No. 09/947,240, filed Sep. 5, 2001, entitled Interconnection Devices, generally relates to interconnection devices that make what is referred to as “temporary” interconnections, which are considered non-permanent. It relates more particularly to electrical connectors, sockets, probes, etc., and more particularly relates to high-density electrical connectors used in test and burn-in done on miniaturized electrical components. More details on this are covered in the original Application, Ref4.
The present invention generally relates to what is referred to as “permanent” interconnections, which include solderable interconnections, and/or mounting of electronic components on boards or on substrates, or on other electronic components and the like.
The present invention is presented in two groups, simply to make it easy to follow, although the two groups can be combined under the one category of permanent interconnections.
The first group relates to leaded electronic components, which have already “leads” or “legs”, and/or electronic components that can be provided with leads to make them look as leaded. It mainly covers the leads of such components and the shapes and orientation of these leads, to enhance the performance of such components. This is generally referred to as “permanent” interconnection.
The second group of the present invention covers in particular interconnections between “lead-less” electronic components and boards and/or substrates, or other similar lead-less components. This is also generally referred to as “permanent” interconnection.
The invention utilizes many of the definitions and items described in the referenced provisional applications as well as the referenced patent application, and it expands on them in the section entitled “DEFINITIONS”.
2. General Background and Prior Art, Applicable to Both Groups
The important background that is common to both groups is the problems resulting from exposing electronic assemblies to varying temperatures, such as thermal cycling or power cycling, or simply from being exposed to harsh environment, including hot and cold temperature environment or to excessive stresses due to shock and vibration.
In the case of leaded electronic components, the first group, like DIP Packages, it has been known that plastic packages are not as reliable as ceramic packages. Plastic packages do not last as long as Ceramic packages. The Military, the Airline Industry and the Telecommunication Industry require that component last some ten to twenty years without failure. These industries specify ceramic leaded components most of the time, because their experience leads them to believe that ceramic components can satisfy these long operating lives, better than plastic components. It has been stated that one of the reasons why plastic leaded components fail prematurely, as compared to ceramic, beside the fact that the plastic materials themselves are not considered “hermetic”, is the occurrence of micro-cracks between the plastic material and the leads or rather the legs. The legs are made of metal, most of the time out of Alloy 22 or other similar metals, which ideally has a TCE that closely matches the TCE of Silicon. Regardless of the material, the legs are usually relatively stiff. After a component is assembled/soldered to its board, it has been noticed that some micro-cracks develop between the legs and the surrounding plastic material. The cracks start at the outside edges of the plastic, right next to the legs, and gradually the cracks migrate inwards and become larger, until they allow moisture and outside atmospheric gases to migrate inwards also towards the chip inside the package. This migration of undesirable materials can damage the chip or at least can make the chip “age” faster. The end result is the failure of the package. It is also believed that thermal cycling accelerates such micro-cracks. The present invention proposes certain solutions that are believed to be able to improve this situation. These solutions will be described later below.
In the case of leadless electronic components, the second group, like the BGAs and the LCCCs, it has been know for a while that soldering such components directly to substrates or to PCBs is not the right thing to do. It can lead to premature failure. This is especially true, when the component is relatively large, i.e. approx. ¼ inch or larger on the side, and when the material of the component is different than that of the substrate, e.g. when the component is silicon or ceramic, while the substrate is FR4, and when the temperature can vary considerably during the life of the assembly. For this reason, several designs have been proposed in the past to counteract the unfavorable effect of such conditions. For example, the inventor, Gabe Cherian, together with other co-inventors, had invented what was called “CCMD”, Chip Carrier Mounting Device, which was later called “Solder Columns” or “Solder Quick”. This is covered by U.S. Pat. Nos. 4,664,309, 4,705,205 and 4,712,721. Other attempts have been made by other inventors, which were more or less successful.
The additional problem nowadays is the fact that many of the components are being miniaturized. The center distances between contact pads are getting smaller and smaller, and the old inventions can no longer keep up with such miniaturization. For example, BGAs have center distances down to 0.020″ (approx. 0.5 mm) and when we consider Chip Scale Packaging, the center distances can be even smaller. The Cherian Solder Columns were originally designed and built to work with 0.050″ (approx. 1.25 mm) center distances. Cherian Solder Columns cannot readily be simply scaled down to size. For this reason, the present invention has addressed this problem and offers solutions as will be described later.